1. Field of the Invention
The present invention relates to a stage device, and more particularly to a stage device adapted for use in an exposure apparatus for manufacturing a semiconductor device, a substrate for a liquid crystal display device, a thin film magnetic head or the like.
2. Related Background Art
In a lithographic process for producing a semiconductor device, substrate for a liquid crystal display device or the like, there is employed a projection exposure apparatus for exposing a photosensitive substrate to the image of a pattern of a photomask or a reticle (hereinafter collectively called reticle) through a projection optical system. Such apparatus is usually provided with a stage device capable of supporting the photosensitive substrate (wafer) and of two-dimensional movement, and the exposure is executed by aligning the reticle and the wafer, through positioning of the stage device to a predetermined position.
Such projection exposure apparatus is placed on an antivibration table, in order to prevent undesirable effect for example on the precision of alignment between the reticle and the wafer, resulting from the vibration of the ground (exterior of the apparatus). Such antivibration table attenuates the vibration from the exterior of the apparatus, by means of an elastic member or a damping member.
FIG. 4 is a schematic view of a conventional projection exposure apparatus.
In the stage device employed in the conventional projection exposure apparatus for semiconductor device production, as shown in FIG. 4, a stage control unit (not shown) drives a motor 4Y provided on an antivibration table 12 constituting a base plate, thereby driving a table 1 to a predetermined position through a feed screw (driving shaft) 3Y. The table 1 supports thereon a wafer W constituting the photosensitive substrate. Onto a desired exposure area on the wafer, light emitted from a light source 20 and directed onto a reticle 18 through an illumination optical system 19, consisting of lens systems such as a fly's eye lens, a condenser lens etc., is projected onto a wafer N by a projection lens 17, whereby a mask pattern is imaged on the wafer. After a projection exposure to the exposure area, the table 1 is suitably moved in such a manner that a next exposure area is positioned in a predetermined position within the projection field of the projection lens 17. An interferometer 7Y measures the position of the table 1, based on the reflected light from a mirror 8Y provided on the table 1.
In such stage device of the conventional configuration, the entire device excluding the table 1 is fixed, as a rigid member, on the antivibration table 12, and the table 1 is fixed, by means of the feed screw 3Y and a guide mechanism (not shown) of the table 1, as a substantially rigid member, to the main body of the device. Stated differently, the table 1 and the device are macroscopically integral, but, in consideration of the comparison of the rigidity of the entire device and the supporting rigidity of the table 1, they are microscopically equivalent to a structural model in which the table is elastically supported on the base plate. This is because, in the requested precision, the feed screw 3Y cannot be regarded as a completely rigid body due to the play and friction in the junction. Because of this fact, the driving (including deceleration and stopping) of the table 1 generates vibration in the entire device excluding the table 1. More specifically, the reaction force of the driving force acting on the table 1 acts on the antivibration table, thereby generating vibration in the entire device excluding the table 1.
However, the table 1 alone tends to remain in the original position by inertia, so that so-called vibration-induced positional aberration is generated between the entire device and the table 1, or between the antivibration table 12 constituting the base plate and the table 1.
In such conventional stage device employed in the projection exposure apparatus for producing semiconductor devices, in driving the table for movement to a predetermined position, there is generated vibration in the entire device, and a positional aberration is generated, resulting from said vibration, between the antivibration table and the table. Since the optical system for projection exposure and the reticle 18 are fixed as rigid members to the base plate as explained before, the positional aberration between the reticle 18 (or the projection optical system 17) and the wafer placed on the table 1 detrimentally affects the performance of the exposure apparatus. For this reason the projection exposure has to be executed after the vibration becomes sufficiently small by spontaneous attenuation, so that the throughput is significantly lowered.